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The organism on the right produced no color, so it does not appear to be a lactose fermenter. MacConkey agar is a selective and differential culture medium for bacteria. It is designed to selectively isolate gram-negative and enteric (normally found in the intestinal tract) bacteria and differentiate them based on lactose fermentation. [1]
This plate is partially inhibitory to Gram (+) bacteria, and will produce a color change in the Gram (-) bacterial colonies based on lactose fermentation abilities. [12] Strong lactose fermenters will appear as dark blue/purple/black, and E.coli (which also ferments lactose) colonies will be dark colored, but will also appear to have a metallic ...
Klebsiella pneumoniae is a Gram-negative, non-motile, encapsulated, lactose-fermenting, facultative anaerobic, rod-shaped bacterium.It appears as a mucoid lactose fermenter on MacConkey agar.
Enterobacteriaceae is a large family of Gram-negative bacteria.It includes over 30 genera and more than 100 species. Its classification above the level of family is still a subject of debate, but one classification places it in the order Enterobacterales of the class Gammaproteobacteria in the phylum Pseudomonadota.
Hektoen enteric agar (HEK, HE or HEA) is a selective and differential agar [1] primarily used to recover Salmonella and Shigella from patient specimens. HEA contains indicators of lactose fermentation and hydrogen sulfide production; as well as inhibitors to prevent the growth of Gram-positive bacteria.
Shigella sonnei can ferment lactose, but only after prolonged incubation, so it is referred to as a late-lactose fermenter. During fermentation of the sugar, acid is formed and the pH of the medium drops, changing the color of the pH indicator. Different formulations use different indicators; neutral red is often used. For example, lactose ...
It is formulated to inhibit Gram-positive bacteria, while the growth of Gram-negative bacilli is encouraged. The colonies of lactose fermenters appear yellow. It is also used to culture possible Salmonella that may be present in a food sample. Most Salmonella colonies produce a black centre on it.
Acinetobacter is a genus of Gram-negative bacteria belonging to the wider class of Gammaproteobacteria. Acinetobacter species are oxidase-negative, exhibit twitching motility, [7] and occur in pairs under magnification. They are important soil organisms, where they contribute to the mineralization of, for example, aromatic compounds.